Maternal Gestational Tdap Vaccination and Autism: A Critique of Becerra-Culqui et al. (2018)

Abstract

We report flaws and inconsistencies in a critically important study of autism risk following maternal Tdap vaccination. The authors of the 2018 study, Prenatal Tetanus, Diphtheria, Acellular Pertussis Vaccination and Autism Spectrum Disorder (BC18), concluded that Tdap gestational vaccination is not associated with increased autism risk and claimed to provide “evidence supporting the ACIP’s recommendation to vaccinate pregnant women”. Our observations, based on information from the study itself, challenge these conclusions. We find evidence of a peculiar study design and approach to data analysis forcing outcomes by arbitrary data adjustments, overlooked variables of importance such as Bordetella pertussis infection prevalence and vaccine injury rates, insufficient consideration of likely interactions between multiple historical medical challenges by vaccines and other interventions on their participants, exclusion from the study individuals likely at risk of vaccine intolerance due to genetics, and indications that the study samples were not representative of the general population. Their first-year data show a concerning spike in ASD rates, and their findings and conclusions did not hold up to real-world data, which currently reports 3.8% ASD rate in California. Our observations, based on information from the study itself, challenge the conclusions of Becerra-Culqui et al, 2018.